Do guys realize when they've messed up?

So I've been with a guy for over 4 months now. one day he told me to ring his friend off his phone so I did. As I clicked on his contacts... A name and number came up of a girl then suddenly disappeared. Anyway as I asked if his phone always deleted contacts. He was confused I then mentioned the girls name. Which he then tried making out I saw another name as the girl turned out to be his ex. He then started to get nasty at me, making out that it's my fault his ex name came up and I'm tryna get into their past... Like wtf. Anyway even the name looked familiar as I saw it on his Snapchat ages ago. Yet he's still denying contact with her even though I've seen it. Anyway we broke up as at some points he was being disrespectful towards me. Then a Couple days later we try rekindle our relationship out wanting to try again but obviously I still had a few questions at the back of my mind about him being in contact with his ex which I wanted to resolve (no harm) now, so there was no conflict about it in the future. But he ended up turning it into an argument asif I had done something wrong which I know full well I hadn't, telling me how he hates his ex and doesn't have any contact with her (he even knows I've Seen it). Telling me to shut the fuck up and getting so rude to me. Blaming me for everything bad in our relationship. Just being cruel. I know I haven't done Anything wrong but I feel though asif I have. As I admit we've had mini arguments on the past which may of pushed us away from eachother but Have I done something wrong? Will he realize he fucked up and come back?